Understanding Complex Flow Pathways within Lab-Scale Denitrifying Bioreactors with a Conservative Tracer

HighlightsStorm size and media age did not significantly impact removal rate based on simulated storm events in lab bioreactors.Post-hoc cluster analysis of bromide tracer time series identified distributed and preferential flow patterns.Distributed flow cluster had significantly higher removal rate and removal efficiency than preferential cluster.Abstract. Denitrifying bioreactors are designed to reduce excess nitrate (NO3-) pollution from agricultural fields. During storm-induced flow events, flow rate and hydraulic retention time (HRT) can fluctuate widely, which may disturb denitrification within bioreactors in ways not captured by current steady-flow models of NO3- removal rate (RR). This study investigated RR and removal efficiency (RE) during storm flows of variable size and duration to close the gap between existing steady-flow models and real-world flow event conditions. Three simulated storm flow events were run through six lab bioreactors, and RR and RE were calculated during and following each event. Our results show that bioreactors were able to attenuate flow such that event size and duration were not significant explanatory variables of RR. A k-means cluster analysis on characteristics of the outflow bromide tracer time series for each bioreactor during each event identified two major flow patterns. The cluster exhibiting a more distributed bromide load through time had a significantly higher average RR than the cluster with a bromide load time series more characteristic of preferential flow (24.8 and 22.0 g N m-3 d-1, respectively, p = 0.01). Bioreactors did not consistently display a given flow pattern but often changed between events. This suggests that flow patterns within lab bioreactors for each event are a more significant driver of RR than the external factor of the inflow hydrograph. Keywords: Denitrifying bioreactor, k-Means clustering, Stormwater, Tracer.

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Estimating traveltimes and groundwater flow patterns using 3D time-lapse crosshole ERT imaging of electrical resistivity fluctuations induced by infiltrating river water

Geophysics ◽

10.1190/geo2011-0328.1 ◽

2012 ◽

Vol 77 (4) ◽

pp. E239-E250 ◽

Cited By ~ 37

Author(s):

Ilaria Coscia ◽

Niklas Linde ◽

Stewart Greenhalgh ◽

Tobias Vogt ◽

Alan Green

Keyword(s):

Electrical Resistivity ◽

Groundwater Flow ◽

River Water ◽

Preferential Flow ◽

Tracer Tests ◽

Time Lapse ◽

Flow Patterns ◽

Bank Filtration ◽

Complex Flow ◽

Drinking Water Production

The infiltration of river water into aquifers is of high relevance to drinking-water production and is a key driver of biogeochemical processes in the hyporheic and riparian zone, but the distribution and quantification of the infiltrating water are difficult to determine using conventional hydrological methods (e.g., borehole logging and tracer tests). By time-lapse inverting crosshole ERT (electrical resistivity tomography) monitoring data, we imaged groundwater flow patterns driven by river water infiltrating a perialpine gravel aquifer in northeastern Switzerland. This was possible because the electrical resistivity of the infiltrating water changed during rainfall-runoff events. Our time-lapse resistivity models indicated rather complex flow patterns as a result of spatially heterogeneous bank filtration and aquifer heterogeneity. The upper part of the aquifer was most affected by the river infiltrate, and the highest groundwater velocities and possible preferential flow occurred at shallow to intermediate depths. Time series of the reconstructed resistivity models matched groundwater electrical resistivity data recorded on borehole loggers in the upper and middle parts of the aquifer, whereas the resistivity models displayed smaller variations and delayed responses with respect to the logging data in the lower part. This study demonstrated that crosshole ERT monitoring of natural electrical resistivity variations of river infiltrate could be used to image and quantify 3D bank filtration and aquifer dynamics at a high spatial resolution.

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OVERLAND FLOW ANALYSIS USING TIME SERIES OF SUAS-DERIVED ELEVATION MODELS

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsannals-iii-8-159-2016 ◽

2016 ◽

Vol III-8 ◽

pp. 159-166 ◽

Cited By ~ 4

Author(s):

J. Jeziorska ◽

H. Mitasova ◽

A. Petrasova ◽

V. Petras ◽

D. Divakaran ◽

...

Keyword(s):

Time Series ◽

Water Flow ◽

Preferential Flow ◽

Overland Flow ◽

Arable Land ◽

Flow Analysis ◽

Sampling Technique ◽

Flow Patterns ◽

Unmanned Aerial Systems ◽

Terrain Models

With the advent of the innovative techniques for generating high temporal and spatial resolution terrain models from Unmanned Aerial Systems (UAS) imagery, it has become possible to precisely map overland flow patterns. Furthermore, the process has become more affordable and efficient through the coupling of small UAS (sUAS) that are easily deployed with Structure from Motion (SfM) algorithms that can efficiently derive 3D data from RGB imagery captured with consumer grade cameras. We propose applying the robust overland flow algorithm based on the path sampling technique for mapping flow paths in the arable land on a small test site in Raleigh, North Carolina. By comparing a time series of five flights in 2015 with the results of a simulation based on the most recent lidar derived DEM (2013), we show that the sUAS based data is suitable for overland flow predictions and has several advantages over the lidar data. The sUAS based data captures preferential flow along tillage and more accurately represents gullies. Furthermore the simulated water flow patterns over the sUAS based terrain models are consistent throughout the year. When terrain models are reconstructed only from sUAS captured RGB imagery, however, water flow modeling is only appropriate in areas with sparse or no vegetation cover.

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OVERLAND FLOW ANALYSIS USING TIME SERIES OF SUAS-DERIVED ELEVATION MODELS

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-iii-8-159-2016 ◽

2016 ◽

Vol III-8 ◽

pp. 159-166 ◽

Cited By ~ 2

Author(s):

J. Jeziorska ◽

H. Mitasova ◽

A. Petrasova ◽

V. Petras ◽

D. Divakaran ◽

...

Keyword(s):

Time Series ◽

Water Flow ◽

Preferential Flow ◽

Overland Flow ◽

Arable Land ◽

Flow Analysis ◽

Sampling Technique ◽

Flow Patterns ◽

Unmanned Aerial Systems ◽

Terrain Models

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Stability Analysis of Hydropower Stations With Complex Flow Patterns in the Tailrace Tunnel

Volume 2, Fora: Cavitation and Multiphase Flow; Fluid Measurements and Instrumentation; Microfluidics; Multiphase Flows: Work in Progress ◽

10.1115/fedsm2013-16617 ◽

2013 ◽

Cited By ~ 1

Author(s):

Jianxu Zhou ◽

Fulin Cai ◽

Ming Hu

Keyword(s):

Free Surface ◽

Stability Analysis ◽

Flow Patterns ◽

Normal Operation ◽

Complex Flow ◽

Diversion Tunnel ◽

Implicit Model ◽

Special Cases ◽

Tailrace Tunnel ◽

Hydropower Stations

For some special tailrace tunnels in the hydropower stations, including the changing top-altitude tailrace tunnel and the tailrace tunnel with downstream reused flat-ceiling diversion tunnel, during normal operation and hydraulic transients, the flow patterns inside are relatively complex mainly including the free-surface pressurized flow and partial free flow if the tail water level is lower than the top elevation of tunnel’s outlet. These complex flow patterns have obvious effect on system’s stability, and can not be simulated accurately by the traditional models. Therefore, a characteristic implicit model is introduced to simulate these complex flow patterns for further stability analysis. In some special cases, the characteristic implicit model also fails to completely simulate the mixed free-surface pressurized flow in the flat-ceiling tailrace tunnel. A new method is presented based on both experimental research and numerical simulation, and then, system’s stability is analyzed by compared with traditional ordinary boundary condition. The results indicate that, with different simulation models for the complex water flow in the tailrace tunnel, system’s dynamic characteristic can be actually revealed with the consideration of the effect of complex flow patterns in the tailrace tunnel on system’s stability and regulation performance.

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Study on De-Nitrification of Improved Step-Feed Progress

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.703.171 ◽

2014 ◽

Vol 703 ◽

pp. 171-174

Author(s):

Bing Wang ◽

Yi Xiao ◽

Shou Hui Tong ◽

Lan Fang ◽

Da Hai You ◽

...

Keyword(s):

Water Quality ◽

Organic Matter ◽

Fluidized Bed ◽

Removal Efficiency ◽

Nitrogen Removal ◽

Removal Rate ◽

Operating Conditions ◽

Removal Mechanism ◽

Aerobic Zone

Improved step-feed de-nitrification progress combined with biological fluidized bed was introduced in this study. The progress had good performance and capacity of de-nitrification and organic matter. The experiment result showed that the de-nitrification efficiency of the improved biological fluidized bed with step-feed process was higher than the fluidized bed A/O process under the same water quality and the operating conditions. When the influent proportion of each segment was equal, the system showed good nitrogen removal efficiency with the change of influent C/N ratio, HRT and sludge return ratio. The removal rate of TN reached up to 88.2%. It showed that the simultaneous nitrification and de-nitrification phenomenon happened in the aerobic zone. The nitrogen removal mechanism was also studied.

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Analysis of long-term water quality changes in the Kis-Balaton Water Protection System with time series-, cluster analysis and Wilks’ lambda distribution

Ecological Engineering ◽

10.1016/j.ecoleng.2010.12.028 ◽

2011 ◽

Vol 37 (4) ◽

pp. 629-635 ◽

Cited By ~ 40

Author(s):

István Gábor Hatvani ◽

József Kovács ◽

Ilona Székely Kovács ◽

Pál Jakusch ◽

János Korponai

Keyword(s):

Water Quality ◽

Time Series ◽

Cluster Analysis ◽

Protection System ◽

Water Protection ◽

Quality Changes ◽

Wilks Lambda

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Assessing dry weather flow contribution in TSS and COD storm events loads in combined sewer systems

Water Science & Technology ◽

10.2166/wst.2011.185 ◽

2011 ◽

Vol 63 (12) ◽

pp. 2983-2991 ◽

Cited By ~ 9

Author(s):

M. Métadier ◽

J. L. Bertrand-Krajewski

Keyword(s):

Time Series ◽

Oxygen Demand ◽

Seasonal Effect ◽

Storm Events ◽

Combined System ◽

Time Step ◽

Urban Catchment ◽

Sewer Systems ◽

Continuous Discharge

Continuous high resolution long term turbidity measurements along with continuous discharge measurements are now recognised as an appropriate technique for the estimation of in sewer total suspended solids (TSS) and Chemical Oxygen Demand (COD) loads during storm events. In the combined system of the Ecully urban catchment (Lyon, France), this technique is implemented since 2003, with more than 200 storm events monitored. This paper presents a method for the estimation of the dry weather (DW) contribution to measured total TSS and COD event loads with special attention devoted to uncertainties assessment. The method accounts for the dynamics of both discharge and turbidity time series at two minutes time step. The study is based on 180 DW days monitored in 2007–2008. Three distinct classes of DW days were evidenced. Variability analysis and quantification showed that no seasonal effect and no trend over the year were detectable. The law of propagation of uncertainties is applicable for uncertainties estimation. The method has then been applied to all measured storm events. This study confirms the interest of long term continuous discharge and turbidity time series in sewer systems, especially in the perspective of wet weather quality modelling.

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Start-Up of A2/O Humic Activated Sludge Systemphosphorus Removal Efficiency Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.113-116.2201 ◽

2010 ◽

Vol 113-116 ◽

pp. 2201-2207 ◽

Cited By ~ 2

Author(s):

Jun Yin ◽

Lei Wu ◽

Ke Zhao ◽

Yu Juan Yu

Keyword(s):

Activated Sludge ◽

Removal Efficiency ◽

Phosphorus Removal ◽

Removal Rate ◽

Phosphorus Uptake ◽

Phosphorus Release ◽

Activated Sludge System ◽

Start Up ◽

Article Analysis ◽

Sludge Activity

In this article, analysis the start-up of A2/O humic activated sludge system phosphorus removal efficiency and the characteristics of anaerobic phosphorus release, aerobic phosphorus uptake, sludge activity and their change in the Series Technologies process. The results show that A2/O humic activated sludge system phosphorus removal rate stabilized at 90.7% ~ 97.6%. Sludge activity except for anoxic zone 2 increased, along the process showed a gradual decrease trend.

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